(endorsed by the i18n WG)
4.6.20 The ruby element
http://dev.w3.org/html5/spec/the-ruby-element.html#the-ruby-element
"A single ruby element, but with no further ruby element descendants"
Does this mean that you can't have a ruby element and additional characters alongside it? For example, since multiple annotations don't always refer to the same sequences of characters, it would be important to ensure you could do the following:
...<ruby><ruby>護<rt>まも</rt></ruby>れ<rt>プロテゴ</rt></ruby>!...
This should result in the rendered text where the hiragana is mono-ruby pronunciation that refers only to the first kanji character, and the katakana is group-ruby that refers to the kanji+hiragana base characters together.
I think that it is clear how this should be parsed, but it must be allowed by the rules in the spec.

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Status: Accepted
Change Description:
https://github.com/w3c/html/commit/40f33a8873b6a4c655a0b6ab79e3deb28078a7ad
Rationale: Adopted WHATWG patch